780 PEOCEEDIXGS OF THE NATIONAL MUSEUM. vol. xxx. 



OH lower side of caudal peduncle. A more or less continuous row of 

 scales runs along the medium line of back, on each side of which is a 

 naked area with or without scales scattered sparsel}^ over it. Naked 

 area may })e continued over top of head, interrupted only by a few 

 scales at occipital region, or top of head may be wholh'^ covered with 

 rough scales to opposite front of eyes. Side of head wholly naked 

 except where scales irregularly cover upper half of opercle and small 

 area on cheek behind eye. Region in front of pectoral naked. 



35. ORESTIAS AGASSIZII Valenciennes. 



Four specimens, from 150 to 165 mm. in length, were collected in 

 Lake Titicaca at Chililaya, Bolivia. 



This species, in proportions of body, stands about midway between 

 the elongate O. pentlandi and O. ciwieri and the short O. alhus and 

 0. hiteux. 



1 have little to add to the description published by Garman." 

 Mouth very small; gape from symphysis of premaxillaries to lower 

 angle of mouth equal to long diameter of orbit; width of snout between 

 lower angles of mouth from 1^ to 1^ times diameter of orbit. The 

 picture published by Cuvier and Valenciennes shows an area in front 

 of pectoral covered with scales. In three of our four specimens this 

 area is entireh' naked; in the other '1 or 3 scales remain and depres- 

 sions indicate the former presence of other scales. It is probable that 

 these scales are lost in the adult tish, as are those on top of snout. 

 The head is contained -1 times in the length to base of caudal, not 4i 

 as in Garman's specimens. 



36. ORESTIAS ALBUS Valenciennes. 



Six specimens from 148 to 155 mm. in length collected in Lake 

 Titicaca. 



This species (at least of the size at hand) may be at once known by 

 the naked area on the upper part of the side, in connection with the 

 short body. 



Length of head, without projecting mandible, 2i to 2f in length to base 

 of caudal. Depth of head at occiput 1\ in length of head, and equal to 

 width of head at opercles, or sometimes a very little less than width of 

 head. Diameter of eye equal to its distance from mouth; H iu snout 

 measured obliquely over top of snout to union of premaxillaries: con- 

 tained 1^ to 1| times in interorbital space. 



Mouth vertical; lower end of gape below level of ej^e. A consider- 

 able amount of variation is exhibited in the squamation. Usually 

 there is a continuous single row of rough plates from the occiput to 

 the dorsal, with a large naked area at each side of it. In some speci- 

 mens, however, the dorsal plates are absent anteriorly and the lateral 



«Mem. Mus. Comp. Zool., XIX, No. 1, 1895, p. 150. 



